Maglev train systems are counted among those transport systems that are distinguished by a vehicle being operated without physical contact on a support system guiding the vehicle in at least one direction. For the guided, contact-free operation, the support system and the vehicle have to physically interact. For this purpose, known systems for example use an air cushion or magnetic forces which are in equilibrium with the weight force or other forces that are acting due to the vehicle or other sources of force. In maglev train systems, rails which predetermine the ability of the vehicle to move in two of three spatial directions are preferably used as support systems. This means that it is only still possible for the vehicle to move in the horizontal orientation of the rail that remains unguided.
In the levitating state, maglev systems move along e.g. on a running surface without any solid friction or hydraulic friction, and therefore allow for low-friction operation that is particularly suitable for high transport speeds. The drive for propelling the vehicle is preferably provided by means of electromagnetic linear motors that also do not have any physical contact, either in the vehicle or in the support system, or also by means of vehicle-side turbomachines.
Magnetically acting levitating train concepts have been known for quite some time. A distinction is made between electrodynamic, electromagnetic and permanent-magnet levitating train systems.
As early as 1911, a first electrodynamic levitating transport system was described in GB 1911 9573, in which a vehicle is kept levitating on an aluminum line by means of periodic or interrupted magnetic fields having repelling forces. Both horizontally and vertically acting magnetic fields are described, said vehicle being propelled by a propeller. In the electrically conductive but non-magnetic line, eddy currents develop in the process. Alternating magnetic fields, caused by the vehicle speed, are absolutely necessary for setting the above-mentioned repelling forces and thus a levitating state.
An electromagnetic maglev train concept was described in 1937 in DE 643 316. In this concept, a vehicle is guided on iron rails, i.e. ferromagnetic rails, in a levitating manner by means of fields generated using electromagnets. The electromagnets are distributed between the rails and on the vehicles. Here, it is essential to regulate the magnetic fields by means of distance control systems, the distance between the rail and the vehicle being determined inductively or capacitively.
DE 39 27 453 C2 describes, by way of example, a permanent-magnetic concept in which passive permanent magnets and soft-iron pole elements are used.
Maglev train systems are thus particularly suitable for producing high-speed trains, in particular for passenger transport. Corresponding systems are already in the test phase and are based on the concepts set out below.
DE 30 04 704 C2 discloses an electromagnetic levitation principle, as has been used in the Transrapid system, for example. The rails are formed by a line that has a laminated iron core and interacts magnetically with vehicle-side horizontally and vertically acting magnetic sources, preferably electromagnets. Forces of attraction act between the line and the magnetic sources, and counteract the weight force and the laterally acting guiding forces of the vehicle in equilibrium. In order to raise the vehicle using forces of attraction, some of the magnetic sources are arranged under the line, i.e. the supports for said magnetic sources engage around the edges of the line. Gap regulation for maintaining the gap width between the vehicle and the rail actively intervenes in the control of the magnetic sources.
Current concepts for a maglev train system use superconducting magnets that magnetically interact with electrically conductive coils and generate a magnetic force that acts counter to said coils. If a superconductor were cooled to below its superconducting transition temperature Tc in an external non-homogeneous magnetic field, the shape of this external magnetic field would be frozen in its present position in the superconductor. Said force is predominantly oriented, depending on the orientation of the magnets, perpendicularly to the rail as a lifting force or in parallel with the rail as a propulsive force.
DE 19 52 757 A describes a superconducting suspension for an electrodynamic levitating transport system. The diamagnetic properties of type I superconductors, such as lead, make it possible for surface currents to build up which generate a magnetic field that counteracts a field acting from the outside.
Likewise, DE 42 04 732 A1 discloses, by way of example, a maglev train in which a plurality of vehicle-side superconducting magnets arranged in series act counter to line-side carrier coils. This approach is also taken in the current maglev system, a Japanese maglev train project between Tokyo and Osaka, Japan, in which a linear motor draws on the coils in order to transmit driving force and braking force to the line.
A basic requirement when using superconductors is producing the required cooling to below the transition temperature Tc. Only in recent years have superconductor materials having a Tc above the boiling point of nitrogen become available, which significantly simplifies, if not entirely facilitates, technological implementation. By combining a magnet with a superconductor having a high transition temperature Tc, magnetic levitation and movement can be achieved, it being possible to utilize the diamagnetism of the superconductor.
DE 102 18 439 A1 describes, by way of example, a magnet arrangement concept for the suspension and guidance of levitating vehicles in which an arrangement of a magnetic-part arrangement and a superconductor arrangement that is physically connected thereto and is made up of one or more superconductors (preferably melt-textured YBaCuO material) is opposite an arrangement of three magnetic rails. Embodiments including a line-side or vehicle-side superconductor arrangement are disclosed. In certain embodiments, the superconducting components are provided with heat-insulating material and/or a layer protecting against oxidation and/or exposure to moisture.